1. Field of the Invention
This invention relates generally to fuel and air metering devices, and, more specifically, to fuel and air metering devices used to effectively control the power output of an externally timed ignition internal combustion engine.
2. Description of the Prior Art
In the past, internal combustion engines have been utilized to provide a mechanical power source for a wide range of applications. Various types of induction apparatus have been developed to provide control over the power output of the engine. Included among those types of apparatus are carburetors and fuel injection systems, which heretofore have utilized a butterfly-type throttle valve to meter the air or the fuel/air mixture. The butterfly throttle valves rotated about an axis generally orthogonal to the direction of flow at the throttle. As the fluid passing the butterfly throttle was constricted through only two variable apertures, flow asymmetries often resulted. A need existed for an air or fuel/air mixture throttle apparatus having a plurality of flow passages to permit a more symmetric distribution of the flow passing the throttle apparatus.
Fuel combustion in an internal combustion engine is a chemical process occurring at the molecular level. Combustion occurs when molecules of fuel combine with molecules of oxygen to release heat. Optimal combustion requires that the liquid fuel be fully vaporized to a molecular state to be associated on a molecular level with oxygen molecules, and also requires that the fuel molecules be thoroughly mixed throughout the oxygen laden intake air. Failure to fully vaporize the fuel reduces engine efficiency and increases unwanted exhaust emissions. A need existed for an apparatus capable of enhancing the vaporization rate of liquid fuel and thoroughly mixing the vaporized fuel with the incoming air.
The fuel consumption rate of an externally timed ignition, such as laser or spark ignition, internal combustion engine has become a growing concern. The fuel consumption rate of an engine is in substantial part a function of the particular fuel/air induction system utilized. For example, when an engine is decelerating a load, as when braking a vehicle down a long grade, the induction systems of the past continued to meter a minimum quantity of fuel, as would be sufficient to maintain the normal engine idle. Since engine braking involves an absorbtion of power by and a dissapation of energy within the engine, the metering of even a minimal quantity of fuel into the engine reduces the power absorbtion and energy dissapation capacity of the engine. Additionally, under conditions where engine braking is desired, the fuel being metered into the engine by the induction system serves no useful purpose or function, and comprises a complete waste of fuel. A need existed for an induction system for an externally timed internal combustion engine capable of conserving fuel by curtailing fuel metering under engine braking conditions.
The mechanically operated induction systems of the past utilized a pressure differential between atmospheric pressure and an accelerated air flow through a venturi to meter fuel, a high pressure pump whose output was controlled by the degree of throttle plate rotation, or a series of high pressure pumps whose output was controlled by the degree of throttle rotation to meter fuel. As each of these systems was expensive, a need existed for a low-cost vacuum controlled fuel metering system.